Oil refining



June 25, 1940. V w. H. BAHLKE Er AL 2205,6113

' OIL HEFINING I Fiied April 29, 1938 550 IV. SCHEl/VE/VAAI,

( torneg Patented June 25, 1940 UNITED STATES OIL REFINING William H.Bahlke, Hammond, Ind., and Fred W.

Scheineman, Chicago, Ill., assignors to StandardOil Company, Chicago,111., a corporation of Indiana Application April 29, 1938, Serial No.205,114

Claims.

This invention relates to anoil refining process and apparatus and itpertains more particularly to the preparation of heavy lubricating oils,bright stocks and/or cylinder stocks from residual petroleum oils orheavy petroleum distillates. This is a continuation-in-part of ourco-pending application Ser. No. 741,052, entitled Oil refining, filedAugust 23, ,1934.

The object of the invention is to remove asphalt m and sludge-formingmaterials from oils containing the same. A further object is to improvethe process of "propane deasphalting and to utilize propane or othernormally gaseous hydrocarbon as a diluent liquid in the acid treatingand neutralization of bright stocks or other lubricants.

Heretofore the acid sludge from heavy lubricating oils has beenextremely difficult to handle, so that its reuse was practicallyimpossible. An object of our invention is to obtain fluid sludge fromheavy oil acid treating,- so that this sludge may be reused for givinganother batch of oil a preliminary acid treatment. Heretofore continuousacid treating processes have only been applicable to gasoline and verylight oils; an object of our invention is to make possible thecontinuous countercurrent acid treating of very heavy oils. A furtherobject is to provide improved apparatus for effecting such continuouscounterourrent acid treating.

When liquefied, normally gaseous hydrocarbons are used in processeswhich result in the formation of corrosive gases, these gases may doserious injury to the propane compressors, condensers, etc. A furtherobject of the invention is to provide a method and means for eliminatingcorrosive gases from the propane before it is returned forreccmpression.

A further object is to provide means for removing propane from acidsludge without unduly imi pairing the consistency of said sludge and theease of handling.

A further object is to provide an improved system for removing moisturewhich is introduced into the system as stripping steam or as neutral- 5izing solution.

A further object is to, provide a process which will minimize acidrequirements, clay requirements, and requirements as to thequality ofthe original lubricating 011 stock undergoingtreat- 5o ment.

Other objects will be apparent from the detailed description of theinvention.

In practicing the invention, we mix propane or the like, preferably in aplurality of stages, with a residual lubricating oil stock, preferablyfrom 5 Mid-Continent crude. We pass this stock with about 2 to 8,preferably 3 to 5, volumes of propane through a continuous asphaltsettler at a temperature of about 1l0-195 F., preferably at about110-115F., and ata pressure of about ,250 to 650 pounds per square inch,removing the asphalt from the lowermost point of the settler andremoving the propane-soluble material from the topmost point thereof. Wethen, preferably after stage. An important feature of the invention isthe use of an efficient system for this countercurrent acid treatment ofthe heavy all stock.

Propane from the acid treating system is neutralized beforebeingreturned to the compressor so 50 that corrosion is minimized. Souroil, preferably in propane solution, is then neutralized with causticand is finally depropanized, the dewaxing and claying being effectedeither before'or after the rem'oval of propane from the oil. The invention will be more clearly understood by reference to the accompanyingdrawing, which is a conventional flow diagram of the improved system.

We will describe the invention as applied to a twenty-five per centMid-Continent residual 0 stock, i. e., a Mid-Continent crude from whichseventy-five percent of the oil has been distilled under non-crackingconditions by the use of steam and/or vacuum distillation. It should beunderstood, however, that the invention is equally applicable to otherviscous oil stocks containing asphaltic, tarry and/or resinous materialsor containing other impurities which are removable by the processhereinafter described. The invention 0 is applicable to heavy distillatestocks such as overhead bright stocks and it is applicable toPennsylvania, Coastal, and other crudes as well as Mid-Continent crudes.

In practicing the invention, we prefer to use propane as theasphalt-precipitating medium and as the diluent and mixing material inthe acid treating step. This propane should not contain ,a large amountof unsaturates such as propylene, ethylene, etc.,-but it may containconsiderable amounts of ethane, butane and the like. It should beunderstood that ethane, butane, etc., may be used instead of propane,provided that the temperature and pressure conditions are suitablyadjusted. The invention may be broadly described as improvements in theapparatus and process of manufacturing bright stock by the use ofliquefied, normally gaseous hydrocarbons.

The twenty-five per cent Mid-Continent resid-' ual stock is withdrawnfrom storage tank In by means of a suitable discharge heater. It isforced through pipe I l by pump I 2 into mixer l3 wherein it is admixedwith propane from line M. This propane may be forced through line ll bypump I5 from propane storage tank l6, but it should be understood thatif storage tank I6 is maintained at sufliciently high pressures the pumpmay be dispensed with.

We prefer to use a plurality of mixers so that the oil is mixed with alittle propane at a time to avoid agglomeration of asphaltic particlesand to provide a solution of the residuum in the propane before enoughpropane is added to cause precipitation of the asphaltic matter. Thusthe material from mixer I3 is passed by line I! to mixer ll into whichare introduced further amounts of propane through line 13. The totalamount of propane which is mixed with the stock will depend to aconsiderable extent on the nature of the stock and the nature of thedesired end products; in the present case 2 to 8 volumes of liquidpropane are employed per volume of residual stock, about 1 part ofpropane being introduced into mixer l3 and 1 to 7 parts being introducedinto mixer l8. The temperature of the propane and the lube stock ispreferably about 110 to 160 F. and the present commercial installationis designed to handle about 1,000 barrels of charging stock per day,which means that about 35 gallons of 011 stock per minute are charged.

The hot mixture of propane and oil stock is then introduced through lineinto asphalt settler 2|, which may be an 8' x 30' pressure vesselmounted in a. substantially horizontal position, or with the outlet endslightly lower than the inlet end. With the present stock and operatingconditions, this settler sustains a pressure of about 650 pounds persquare inch and it is, of course, equipped with suitable pressure andtemperature gauges and with a loaded pressure release valve whichdischarges into a gas line in case the pressure becomes dangerouslyhigh.

An interface liquid level is usually maintained within this settler,preferably about one-fourth to one-third of the distance from the bottomto the top and when the nature of the precipitate asphalt permits, thisliquid level is maintained by a float 2 IA which controls valve 213 inasphalt drawoi'f line 22, which is placed at the lowermost point of thesettler.

It should be understood that instead of using a horizontal pressure drumfor efl'ecting this deasphalting step we may use a verticalcountercurrent baffled tower, in which case we will introduce the hotresiduum at the top of the tower and introduce the propane at the bottomof the tower; this will not only serve to give a gradual mixing of thepropane with the residuum. but it will give excellent countercurrentdeasphalting and it will result in the elimination of an extremely dryasphalt from which substantially all of the desirable lubricating oilhas been removed.

The propane solution of deasphalted oil is discharged from the settlerthrough line 23 through release valve 23A into mixer 24 wherein it isadmixed with acid sludge from line 25. Heretofore it has been impossibleto employ countercurrent acid treating processes for extremely heavyoils because the character of the acid sludge has been such thathandling and mixing with incoming stock was impossible. We havediscovered that in our propane process the sludge is sufiiciently mobileand fluid that it may be readily pumped through line 25 to mixer 24 andit may be utilized to remove a large amount of the impurities from theoil stock before said stock is treated with fresh acid. It should benoted that the release of pressure immediately preceding mixer 24 causesa violent and turbulent flow through said mixer and thus facilitates andinsures a thorough mixture of the oil with the sludge. The reduction ofpressure also causes a cooling effect due to the vaporization of aportion of the propane. This cooling effect, or self-refrigeration, isof importance as better eiliciency of acid treatment is obtained on someoils when the temperature is reduced.

This oil sludge mixture is introduced by pipe 26 into the upper part ofsettler 21, which operates at a temperature of about 110 F. and apressure of about 200 pounds per square inch and which may be a verticalpressure vessel about 6' in diameter and 20' high. The lowered pressurecauses an extremely turbulent condition in the settler and, in order toprevent this turbulent condition from interfering with quiescentsettling, we provide a funnel-shaped bailie 28 terminating in a centraldownwardly extending pipe 29 which extends into the body of acid treatedoil. A vent pipe 30 is provided for releasing gases which accumulatebetween the liquid level in the settler and the under side of theconical or funnel-like bailie 28. Propane may be removed from the top ofthe settler through pipe 3|.

In the base of settler 21 we maintain a quiescent body of sour oil andsludge-more specifically, an oil level 32 and a sludge level 33. Sludgeis withdrawn from the base of the settler through line 34 in amountsregulated by valve 35, which is controlled by float 36 or by othersuitable liquid level control apparatus. Sour oil is withdrawn throughline 31 in amounts regulated by valve 38 which is controlled by float 39or other suitable liquid level control apparatus. The sour oil isintroduced into mixer 40 wherein it is intimately mixed with fresh acidfrom line ll, preferably about .25 to .75 pound of 93% sulfuric acid pergallon of oil (although various quantities and concentrations will berequired for various other oil stocks, as is well known to those skilledin the fleld of petroleum refining).

The mixture of oil with fresh acid is introduced through line 42 intosettler 43. which is identical in structure with settler 21. It shouldbe noted that any heat evolved by the chemical reaction of the acid withcertain constituents in the 011 does not causenany appreciable increasein the temperature of the oil, as suflicient propane will vaporize tokeep the temperature practically constant. By proper control of pressurein settler 43 it will be possible to carry out the acid treatment at anydesired temperature not exceeding that of the oil entering mixer 40. Thesludge from the base of settler 43 is passed by line 44 and pump 4! toline 25 for admixture with the propane-oil solution in mixer 24, ashereinabove described. This reuse of acid sludge for treating furtheramounts of oil-is unique in the treating of bright stock and isattributable to the remarkable effect of the propane as a fluxingmedium. Heretofore acid sludge from such heavy oils has been so nonfiuidand contaminated with coke and tarry matter that its reuse has beenimpossible. It is needless to point out that this countercurrent acidtreating of bright stocks results in the saving of large quantities ofboth acid and clay.

Propane from settlers 21 and 43 may contain sulfur dioxide or othercorrosive gases and we therefore pass them through line 45 to wash tower41 and scrub them with caustic from line 48 before passing them throughline 49 to condenser 50. The wash tower may be a 3' x 9' bailledpressure vessel and it may be provided with a circulating line 5| andpump 52 for recirculating the caustic-also with line 53 for withdrawingused caustic. In apparatus operated at lower'pressures it may benecessary to compress the propane gases before passing them to thepropane condensers and in such cases it is especially important thatsulfur dioxide and other corrosive gases be removed from the propane.

The caustic used in wash tower 41 may be obtained from caustic storagetank 54 and caustic from this tank may be introduced through pump 55 andline 55 to mixer 51 for intimate admixture with sour oil from settler 43and line 58. This mixture of neutralized diluted oil is then passedthrough line 59 to caustic settler 50, which may be a horizontal 5' x30' drum mounted in a slightly inclined position as described inconnection with asphalt settler 2 l. The caustic wash liquor iswithdrawn through line 5| in amounts regulated by valve 52, which isoperated by float 53. The neutralized oil is withdrawn from the oppositeand upper end of the settler through line 54, from which it may beintroduced into suitable dewaxing means or clay treating means (notshown). The propane with which the oil is diluted may be utilized bothas a diluent and as a refrigerant in the dewaxing step and/or it may beused as a diluent in the clay percolation step. In the dewaxing processthe propane has been found to greatly improve filtering and settlingrates and in the clay treating processes it has been found to greatlyimprove the clay yields. Both of these processes per se are old and theywill therefore not be described in detail in this case. 4

Finally, the finished oil which is still in propane solution isintroduced through line 55 to oil still 55, which may be heated byclosed steam coils 51. The propane may be removed through line 58directly to condenser 50 because still 551s preferably maintained at apressure of about 200 pounds per square inch and the temperature in thebase of this still is preferably about 250 F. Hot oil from the base ofthe still may be passed through line 59 in reducing valve 10 to stripper.1 l at about 35 pounds pressure and the last traces of propane may beremoved by the introduction of stripping gas such as steam through line1'2. The finished oil may be withdrawn through line I3 to storage. 1

Propane and steam from stripper Il may be passed through line 14 andline E5 to stripping jet condenser 15 wherein the stripping steam iscondensed and separated from the propane, the former passing throughline 11 to the sewer and the latter passing through line 18 and line 19to dry drum which acts as a water trapout, any remaining water beingwithdrawn therefrom through line 8|. Propane from dry drum 80 is passedthrough line 82 to compressor 83 and thence through line 84 to propanecondenser 50.

Asphalt from settler 2| is withdrawn through line 22 to asphalt still85, which is provided with steam heater coil 85 and which is likewisemaintained at a pressure of about 200 pounds. Propane from the top ofthis still is passed by line 81 directly to propane condenser 50.Asphalt from the bottom of still 85 is passed through line-88 andreducing valve to stripper 90, open steam being introduced through line9I'and finished asphalt being withdrawn through line 92. The propane andsteam from the top ofstripper 90 is introduced through line 93 and line15 to stripping jet condenser 15, from which the propane follows thecourse hereinabove described.

' which would be almost impossible to handle. We

have discovered, however, that by mixing gas oil from line 94 with thisacid sludge from line 34 and introducing the mixture of gas oil and acidsludge into sludge still 95, we may drive off practically all of thepropane by means of open steam or closed steam coils 95 and we may-thenwithdraw the gas oil-sludge mixture to the acid works through line 91.Propane is removed from sludge still 95 through line 98 to neutralizingcondenser 99 through which we prefer to circulate an aqueous causticsolution'by means of pump I00 and line l0l. Water is introduced intostripping jet condenser through line I02 and fresh caustic is-introducedinto the neutralizing condenser through line I03, the used caustic beingwithdrawn through line I04. Propane from neutralizing condenser iswithdrawn through line and passed through line 19 to dry drum 80, fromwhich the propane is passed to the compressor and condenser ashereinabove described.

In the above process we prefer to use a deasphalting temperature of1l0-ll5 F., but it should be understood that we may employ othertemperatures, depending upon the nature of the oil undergoing thedeasphalting treatment, the nature of the desired end products, theamountof propane employed, etc. As a general rule, we may operate at anytemperature between about 100 F. and the critical temperature of theliquefied, normally gaseous hydrocarbon. In the case of propane, we mayuse any temperature between 100 F. and 200 F., but we prefer, ashereinabove described, to operate at about F.

For-a clearer understanding of the effect of propane-to-oil ratios andoperating temperatures on Mid-Continent residual oil stock, we willdescribe results obtained from the systematic investigation made witha'300 viscosity M. C. residual stock. In this investigation thepropaneto-oil ratio was varied from 2.3 to 9.0 volumes of propane pervolume of oil at temperatures of 100 F., 165 F., and F. At 100 F. theyield of deasphalted' oil decreased with increasing propane ratio and asthe yield decreased the viscoslty of the recovered oil decreased, whilethe color of the oil was improved. At 165 F. the yield of oil recoveredwas much lower than that at 100 F., but the yield increased withincreasing propane concentration. Moreover, at 165 F. the viscosity ofthe recovered oil remained substantially constant with increasingpropane ratio, but the color of the oil was very markedly improved bylarger propane ratios. At 190 F. the general comparative effect was thesame as at F. The results of our experiments may be tabulated asfollows:

Temperatures, 100 I Propane to oil ratio Percent Color Vls. at yield No.210

2. 94 m 4. 87 g? 9. 80 l 165 Propane to oil ratio Percent Color Vis. atyield N 0. 210

Propane to oil ratio Percent Color Vis. at

old N 0. 210

Note.All color units are Tag Robinson-R (diluted).

These results should be sufllcient to teach one skilled in the art thegeneral trends to be expected in propane deasphalting and the particularoperating conditions in any case must be based on preliminaryexperiments with the oil to be treated.

While we have described in detail a preferred embodiment of ourinvention, it should be understood that we do not limit ourselves to anyof the details hereinabove set forth except as defined by the followingclaims which should be construed as broadly as the prior art willpermit.

We claim:

1. In a lubricating oil refining system, a high temperature highpressure asphalt settler, means for introducing oil and propane intosaid asphalt settler, an acid sludge settler, means for introducing apropane-oil solution from the asphalt settler to the acid sludgesettler, means for admixing a fluid sludge with said propane-oil mixtureas it flows from said asphalt settler to said acid sludge settler, meansfor withdrawing acid sludge from the base of said sludge settler, meansfor diluting said sludge with a normally liquid hydrocarbon, means forremoving gases from said diluted sludge, means for neutralizing theremoved gases, means for returning the neutralized gases forintroduction with further amounts of oil into said asphalt settler meansfor withdrawing souroil from said sludge settler and for mix-- thepresence of at least three volumes of propane per volume of oil,settling the sludge, neutralizing the oil in propane solution, anddemopanizing said neutralized oil, diluting said sludge with a normallyliquid hydrocarbon diluent, stripping propane out of said sludge withsteam, neutralizing said propane with caustic and returning saidneutralized propane to the system.

3. The method of claim 2 wherein open steam is used for the, sludgestripping step.

4. The method of claim 2 wherein closed steam is used for the sludgestripping step.

5. The method of refining a viscous mixed base lubricating oil stockwhich comprises deasphalting it with about 3 to 5 volumes of propane ata temperature of about 1l0-ll5 F., separating and depropanizing theasphalt layer, acid treating the propane-soluble layer in the presenceof at least 3 volumes of propane per volume of oil, separating thesludge, diluting the sludge with a normally liquid hydrocarbon diluent,depropanizing said diluted sludge with steam, scrubbing the propane fromthe sludge-depropanizing step with a caustic solution, returning thescrubbed propane for admixture with further amounts of the oil stock tobe refined, neutralizing the acid treated oil, and depropanizing said011.

